Fuel injection apparatus for externally ignited internal combustion engines operating on continuously injected fuel

ABSTRACT

In a fuel injection apparatus in which an air sensor deflected as a function of the intake air quantities maintains the air-tofuel ratio at a constant value and wherein the return force affecting the air sensor and opposing the deflecting force of the air flow is derived from pressurized liquid, there is provided a control valve for altering the pressure of said liquid; the setting of said control valve is determined by a primary spring, the bias of which is varied as a function of engine parameters and by an opposing secondary spring, the bias of which is varied as a function of the oxygen content of the exhaust gas for the purpose of maintaining therein an air ratio lambda close to 1.

Ilite tates Ecltert [75] Inventor: Konrad Eckert, i

Stuttgart-Feuerbach, Germany [73] Assignee: Robert Bosch GmbH, Stuttgart,

Germany [22] Filed: Sept. 18, 1972 [21] Appl. No.: 289,841

[30] Foreign Application Priority Data Sept. 17, 1971 Germany 2146506 [52] US. CL. 123/119 R, 123/32 AE, 123/140 MC, 123/139 AW [51] Int. Cl. F02m 69/00 [58] Field of Search 123/140 MC, 119 R; 60/276 [56] References Cited UNITED STATES PATENTS 2,244,669 6/1941 Becker 123/140 MC FUEL INJECTION APPARATUS FOR EXTERNALLY IGNITED INTERNAL COMBUSTION ENGINES OPERATING ON CONTINUOUSLY INJECTED FUEL 3,680,535 8/1972 Eckcrt et all. 1. 123/1 19 R Primary ExaminerLaurence M. Goodridge Attorney, Agent, or Firm-Edwin E. Greigg [5 7 ABSTRACT In a fuel injection apparatus in which an air sensor deflected as a function of the intake air quantities maintains the air-to-fuel ratio at a constant value and wherein the return force affecting the air sensor and opposing the deflecting force of the air flow is derived from pressurized liquid, there is provided a control valve for altering the pressure of said liquid; the setting of said control valve is determined by a primary spring, the bias of which is varied as a function of engine parameters and by an opposing secondary spring, the bias of which is varied as a function of the oxygen content of the exhaust gas for the purpose of maintaining therein an air ratio A close to 1.

3 Claims, 1 Drawing Figure 1 EXHAUST PIPE FUEL INJECTION APPARATUS FOR EXTERNALLY IGNITEI) INTERNAL COMBUSTION ENGINES OPERATING ON CONTINUOUSLY INJECTED FUEL BACKGROUND OF THE INVENTION This invention relates to a fuel injection apparatus that continuously injects fuel into the suction tube of an externally ignited internal combustion engine and is of the type which includes an air sensor disposed in the suction tube and spaced from an arbitrarily operable butterfly valve. The air sensor is deflected against a constant return force by and as a function of the throughgoing air quantities and actuates the valve member of a fuel metering valve for metering fuel quantities in proportion to the air quantities. The return force is derived from pressurized liquid which is supplied under constant, but arbitrarily variable pressure through a pressure conduit and affects a forcetransmitting member coupled to the air sensor. For regulating the return force there is provided a flat seat valve having a movable valve member constituted by a diaphragm which is loaded by a primary spring, the bias of which is variable as a function of engine parameters.

The exhaust gases of internal combustion engines contain among others, carbon monoxide, nitrogen oxides and uncombusted or partially combusted hydrocarbons which pollute the air to a significant degree. In order to substantially convert the harmful pollutants of the exhaust gas to harmless compounds, the exhaust gas is passed at a temperature of about 600 C through catalyzers. In such a procedure it is necessary that the exhaust gas have a composition which permits a practically complete conversion into harmless compounds, that is, the air-to-fuel ratio has to be approximately stoichometrical or, stated differently, the air ratio should be close to l.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide an improved fuel injection apparatus of the aforenoted type wherein the aforenoted favorable air ratio It is effected by an additional change in the return force exerted on the air sensor.

Briefly stated, according to the invention, there is provided a secondary spring which opposes the aforenoted primary spring and the bias of which is variable as a function of the air ratio in the exhaust gas of the internal combustion engine.

The invention will be better understood, as well as further objects and advantages become more apparent, from the ensuing detailed specification of a preferred, although exemplary, embodiment taken in conjunction with the sole figure illustrating the invention in schematic longitudinal section.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the sole FIGURE, the intake air enters from the left into a suction tube portion 1 and then flows into a conical suction tube portion 2 in which there is movably disposed an air sensor 3. Therefrom the air passes through a connecting hose 4 into a suction tube portion 5 which contains an arbitrarily operable butterfly valve 6. Therefrom the intake air flows to one or more cylinders of the internal combustion engine with which the fuel injection apparatus is associated. The air sensor 3 comprises a plate member 3 disposed normal to the direction of air flow and is movable by, and as an approximately linear function of, the air quantities passing through the suction tube. Assuming a constant return force on the air sensor 3 (that is, a return force which is independent from the position of the air sensor 3) and further assuming a constant air pressure upstream of the air sensor 3, the pressure prevailing between the air sensor 3 and the butterfly valve 6 will also be constant.

The air sensor 3 directly controls a fuel metering and quantity distributor valve 7. For this purpose, the motion of the air sensor 3 is transmitted to the valve 7 by a lever 8 connected with the air sensor plate and supported by a pivot pin 9. During the pivotal motion of the lever 8, its nose 10 displaces a movable valve member 11 which forms part of the fuel metering and quantity distributor valve 7 and which is shaped as control plunger. The radial face 12 of the control plunger 11 disposed remote from the nose 10 of the lever 8 is exposed to pressurized liquid, which serves as the return force affecting the air sensor 3.

The fuel is supplied to the fuel injection apparatus by means of a fuel pump 15 which is driven by an electromotor 14 and which draws fuel from a fuel tank 16 and drives it to the fuel metering valve 7 through a conduit 17. From the latter there extends a conduit 18 in which there is situated a pressure limiting valve 19.

From the conduit 17 the fuel is admitted into a channel 22 in the housing of the fuel metering and distributor valve 7. The channel 22 leads to an axially long annular groove 23 provided in the control plunger 11 and further, through a plurality of ports, to individual chambers 24 each bounded by a portion of a sole diaphragm 25. In this manner one side of the diaphragm 25 is exposed to the pressure of the fuel. Dependent upon the position of the control plunger 11, a control edge 11a bounding the annular groove 23 overlaps to a greater or lesser extent the control slots 26 each of which communicates through an associated channel 27, with a chamber 28 separated from an associated chamber 24 by the diaphragm 25. From the chamber 28 the fuel is admitted through channels 29 to the individual fuel injection valves (not shown) which are disposed in the suction tube in the vicinity of the engine cylinders. The diaphragm 25 serves as the movable valve member of a flat seat valve which, when the fuel injection apparatus is not operational, is maintained in an open position by means of a spring 30. The dia phragm boxes, each formed of a chamber 24 and a chamber 28 and each including a flat seat valve, ensure that independently from the extent of overlap between the annular groove 23 and the control slots 26, that is, independently from the fuel quantities passing to the fuel injection valves, the pressure drop across the fuel metering valve 23, 26 remains substantially constant.

Upon pivotal motion of the lever 8, the air sensor plate 3 is moved as a function of the throughgoing air quantities in the conical portion 2, so that the annular flow passage section defined by the periphery of the air sensor plate and the inner wall of the conical portion 2 is proportionate to the deflection of the air sensor 3. With this assumption given, there exists a linear dependence between the deflection of the air sensor 3 and the displacement of the control plunger 11, so that to the air quantities passing through the suction tube there are added continuously proportionate fuel quantities.

The pressurized liquid which exerts a force on the control plunger 11 is fuel taken from the fuel circuit. For this purpose, from the conduit 17 there extends a conduit 33 which opens into a pressure chamber 34 through a throttle 56. Into the latter there projects that portion of the control plunger 11 that includes the terminal radial face 12. In the conduit 33 there is disposed a throttle 35 which separates the supply circuit 17 of the fuel metering valve 7 from the control pressure circuit now to be described.

From the conduit 33, downstream of the throttle 35, there extends a conduit 36 which leads to a regulating mechanism 37 which is formed as a flat seat valve. Its movable valve member is constituted by a diaphragm 41 which cooperates with a stationary valve seat 42. A very slight displacement of the diaphragm 41 is sufficient to fully open this valve and allow the fuel to pass therethrough from the pressure conduit 36 and flow in a depressurized condition through a conduit 38 back into the fuel tank 16.

The diaphragm 41 is loaded by a primary spring 43, the bias of which is a function of the position of the butterfly valve 6. For this purpose there is provided a cam disc 44 which is affixed to the shaft 45 of the butterfly valve 6. The cam disc 44 is in engagement with a follower pin 46, the movement of which is transmitted through a cup-shaped spring seat member 47 to the primary spring 43. On that side of the diaphragm 41 which is facing away from the primary spring 43 there is exerted the force of a secondary spring 48 supported at its other end by a magnet armature 49. The latter slides on a sleeve 50 in the inside ofa solenoid 51 and is urged by the secondary spring 48 into contact with a first abutment 52 when the solenoid 51 is in a de-energized condition. In the energized condition of the latter the armature 49 is urged by the electromagnetic forces into engagement with a second abutment 54, overcoming the force of spring 48. The magnetic circuit is closed by a solenoid casing 53.

The aforedescribed fuel injection apparatus operates in the following manner:

When the internal combustion engine is running, the fuel pump driven by the electromotor l4 draws fuel from the fuel tank 16 and drives the same through the conduit 17 to the fuel metering valve 7. Simultaneously, the internal combustion engine draws air through the suction tube 1, 2, 4, 5. As a result, the air sensor 3 is deflected from its position of rest to a certain extent. As a function of the magnitude of such deflection, the lever 8 displaces the control plunger 11 which, with its control edge lla, increases the flow passage section at the control slots 26. The direct connection between the air sensor 3 and the control plunger 11 results in a constant ratio between the air quantities and the metered fuel quantities.

In order to maintain the fuel-air mixture at a leaner or richer level as a function of the operational range of the internal combustion engine, it is necessary to vary the constant return force on the air sensor 3 as a function of engine parameters, such as the engine load, characterized, for example, by the angular position of the butterfly valve. Accordingly, such a change in the constant return force is effected by displacing, as a function of the angular position of the butterfly valve 6, the follower pin 46 by the cam disc 44. In this manner the bias of the primary spring 43 is also altered, resulting in a change in the pressure of the pressurized liquid in the pressure chamber 34.

In order to enhance the efficiency of the catalyzer disposed in the path of the exhaust gas, there must be ensured an air ratio A that is close to 1. To achieve this result it is necessary to continuously monitor the air ratio in the exhaust gas and to regulate the metering operation of the fuel metering valve 7 accordingly. For monitoring the air ratio in the exhaust conduit, there may be provided an oxygen sonde, which, by means of an amplifier circuit, supplies the control current for the regulating mechanism 37 formed as a two-point regulator. During the energized condition of the electromagnet 51, 53 the armature 49 is drawn to the abutment 54 whereby the bias of the secondary spring 48 working against the primary spring 43 is increased and thus the pressure in the control pressure circuit 33, 36 and in the pressure chamber 34 is lowered, resulting in the metering of increased fuel quantities. The pressure of the pressurized liquid and thus the metered fuel quantities may be regulated within relatively narrow limits by virtue of the aforenoted two-point regulation.

The two-point regulation may also be used for controlling the addition of an excess fuel quantity for starting a cold engine, particularly if there is no requirement for steplessly controlling the operation of the hot engine. For such a mode of application the regulating mechanism 37 operates, in an operational range limited in time, not as a regulating mechanism, but as a control mechanism.

That which is claimed is:

1. In a fuel injection apparatus for the continuous injection of fuel into the suction tube of an internal combustion engine, said suction tube containing an arbitrarily operable butterfly valve, said apparatus being of the known type that has a. an air sensor member forming part of an air sensor means disposed in said suction tube spaced from said butterfly valve, said air sensor member being deflected by the flow of intake air as a function of the intake air quantities,

b. lever means forming part of said air sensor means and being attached to said sensor member,

0. means generating a return force affecting said air sensor means and opposing the deflecting force of the air flow, said return force being independent from the deflected position of said air sensor member, said means including a pressure chamber filled with pressurized liquid supplying said return force,

. a fuel metering and distributor valve having a movable valve member exposed to the pressure of said liquid and operatively connected to said lever means to be displaced thereby against said return force to an extent proportionate to the deflection of said air sensor member for maintaining constant the fuel-to-air ratio for any given return force,

e. a control valve means varying said return force, said control valve means having a movable valve member loaded by a primary spring and f. means varying the bias of said primary spring as a function of at least one engine parameter, the improvement comprising a secondary spring connected to said movable valve member of said control valve means and means for varying the bias of said secondary spring as a function of the air ratio in the exhaust gas of said internal combustion engine, wherein said control valve means is formed as a flat seat valve and its movable valve member is constituted by a diaphragm, and wherein said primary spring exerts a force on one side of said diaphragm and said secondary spring exerts an opposing force on the other side of said diaphragm,

2. In a fuel injection apparatus for the continuous injection of fuel into the suction tube of an internal combustion engine, said suction tube containing an arbitrarily operable butterfly valve, said apparatus being of the known type that has a. an air sensor member forming part of an air sensor means disposed in said suction tube spaced from said butterfly valve, said air sensor member being deflected by the flow of intake air as a function of the intake air quantities,

b. lever means forming part of said air sensor means and being attached to said sensor member,

c. means generating a return force affecting said air sensor means and opposing the deflecting force of the air flow, said return force being independent from the deflected position of said air sensor member, said means including a pressure chamber filled with pressurized liquid supplying said return force,

d. a fuel metering and distributor valve having a movable valve member exposed to the pressure of said liquid and operatively connected to said lever means to be displaced thereby against said return force to an extent proportionate to the deflection of said air sensor member for maintaining constant the fuel-to-air ratio for any given return force,

e. a control valve means varying said return force,

said control valve means having a movable valve member loaded by a primary spring, and

. means varying the bias of said primary spring as a function of at least one engine parameter, the improvement comprising a secondary spring connected to said movable valve member of said control valve means and means for varying the bias of said secondary spring as a function of the air ratio in the exhaust gas of said internal combustion engine, said means for varying the bias of said secondary spring including an electromagnet having a solenoid and an armature displaceable by electromagnetic forces generated by said solenoid and means for energizing said solenoid, said secondary spring being in engagement with said armature with the bias of said secondary spring being varied as a function of the position of said armature.

3. An improvement as defined in claim 2, wherein the means for varying the bias of said secondary spring further includes a first abutment against which said armature is pressed by said secondary spring in the deenergized condition of said solenoid and a second abutment against which said armature is pressed by electromagnetic forces in the energized condition of said solenoid. 

1. In a fuel injection apparatus for the continuous injection of fuel into the suction tube of an internal combustion engine, said suction tube containing an arbitrarily operable butterfly valve, said apparatus being of the known type that has a. an air sensor member forming part of an air sensor means disposed in said suction tube spaced from said butterfly valve, said air sensor member being deflected by the flow of intake air as a function of the intake air quantities, b. lever means forming part of said air sensor means and being attached to said sensor member, c. means generating a return force affecting said air sensor means and opposing the deflecting force of the air flow, said return force being independent from the deflected position of said air sensor member, said means including a pressure chamber filled with pressurized liquid supplying said return force, d. a fuel metering and distributor valve having a movable valve member exposed to the pressure of said liquid and operatively connected to said lever means to be displaced thereby against said return force to an extent proportionate to the deflection of said air sensor member for maintaining constant the fuel-toair ratio for any given return force, e. a control valve means varying said return force, said control valve means having a movable valve member loaded by a primary spring and f. means varying the bias of said primary spring as a function of at least one engine parameter, the improvement comprising a secondary spring connected to said movable valve member of said control valve means and means for varying the bias of said secondary spring as a function of the air ratio in the exhaust gas of said internal combustion engine, wherein said control valve means is formed as a flat seat valve and its movable valve member is constituted by a diaphragm, and wherein said primary spring exerts a force on one side of said diaphragm and said secondary spring exerts an opposing force on the other side of said diaphragm.
 2. In a fuel injection apparatus for the continuous injection of fuel into the suction tube of an internal combustion engine, said suction tube containing an arbitrarily operable butterfly valve, said apparatus being of the known type that has a. an air sensor member forming part of an air sensor means disposed in said suction tube spaced from said butterfly valve, said air sensor member being deflected by the flow of intake air as a function of the intake air quantities, b. lever means forming part of said air sensor means and being attached to said sensor member, c. means generating a return force affecting said air sensor means and opposing the deflecting force of the air flow, said return force being independent from the deflected position of said air sensor member, said means including a pressure chamber filled with pressurized liquid supplying said return force, d. a fuel metering and distributor valve having a movable valve member exposed to the pressure of said liquid and opEratively connected to said lever means to be displaced thereby against said return force to an extent proportionate to the deflection of said air sensor member for maintaining constant the fuel-to-air ratio for any given return force, e. a control valve means varying said return force, said control valve means having a movable valve member loaded by a primary spring, and f. means varying the bias of said primary spring as a function of at least one engine parameter, the improvement comprising a secondary spring connected to said movable valve member of said control valve means and means for varying the bias of said secondary spring as a function of the air ratio in the exhaust gas of said internal combustion engine, said means for varying the bias of said secondary spring including an electromagnet having a solenoid and an armature displaceable by electromagnetic forces generated by said solenoid and means for energizing said solenoid, said secondary spring being in engagement with said armature with the bias of said secondary spring being varied as a function of the position of said armature.
 3. An improvement as defined in claim 2, wherein the means for varying the bias of said secondary spring further includes a first abutment against which said armature is pressed by said secondary spring in the de-energized condition of said solenoid and a second abutment against which said armature is pressed by electromagnetic forces in the energized condition of said solenoid. 